The online retailer's latest numbers come on the back of a loss in the second quarter, as well.

Shares sank nearly 8 percent early Friday, with the stock now down about 28 percent for the year, compared with a year-to-date rise of 6 percent for the S&P 500 index.

The disappointing results mark the latest turn in the roller coaster ride that is Amazon's performance, which has swung between profits and losses due to its strategy of investing in new areas, including a smartphone, tablets and cloud-computing data centers. Investors have generally accepted the strategy, with the understanding that a payoff would come down the line. As a result, the company's heavy spending hadn't affected its shares much -- until this year. Investors now appear to have lost their patience with Amazon's unimpressive bottom line.

In theory, the company could be forced rein in its spending to appease investors, but that doesn't seem likely, as third-quarter results showed a 23 percent rise in operating expenses year over year to $21.1 billion. It will be hard to put the brakes on that level of spending.

Despite investors turning their backs on Amazon, several analysts said Friday that the long-term picture for the company remains strong, with revenue continuing to grow and Amazon likely bringing more customers into its Prime premium membership program. (Amazon, however, doesn't disclose how many customers are on Prime.) For the latest quarter, the company posted $20.6 billion in sales, up 20 percent from a year ago.

If Amazon's stock continues to slide, Macquarie Research's Ben Schachter predicts, the company could end up with an activist investor on its hands, agitating for major changes. Amazon could also hurt its ability to attract and retain top-notch employees with a dropping stock, he said.

On the company's call with analysts Thursday night, Amazon finance chief Tom Szkutak repeatedly referenced the importance of the company being "judicious" and "selective" in its future investments.